ixampl now supports insertions

While I haven't tested it exhaustively, my implementation now supports 
insertions:


ixml
      1 numbers: @source, n**-", ".
      2 source: +"ixml".
      3 n: neg; pos.
      4 -neg: -"(", +"-", d+, -")".
      5 -pos: +"+", d+.
      6 -d: ["0"-"9"].

input
      1 123, (456), 7, (8), 9
result
<numbers source='ixml'>
    <n>+123</n>
    <n>-456</n>
    <n>+7</n>
    <n>-8</n>
    <n>+9</n>
</numbers>

end